Resistance material



Ohms

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hburs Cur/n Curves for HZLamp-B/ac/ ,Cmcrefe unuoo |u..| LIN-HUI- R. W. STEABNS. RESISTANCE MATERIAL. APPLICATION msol'rza. I9, lqzo.

Patented Oct. 25, 1921. Q

k L Q (J 29% 20% Figl.

(Ampere) 1 0/1 Chamcferiafic Cur-res 21 amp -B/ack Con'cr-efe Jr a 1.9 20 2/ 22 2a 24 25 Percemages of Lamp-Black In Vern-l: or

Ralph W. Stearfns,

His Attorny [IL/w Pa ronounced, or are very expensive to manu- UNITED STAT nrsisrmcn Application filed February 1 To all 'wlwmit may concern:

Be it known that I, RALPH W. STEARNS, a citizen of the United States, residing at schenectagy, in the county of Schenectady, State of ew York, have invented 061138111 new and useful Improvements in Resistance Material, of which the following is a specification.

My invention relates to resistance material and has for its object a substantially uniform product with desired electrical characteristics produced in a simple and economical manner.

Specifically, my invention relates to the roduction of a lastic resistance material aving a so-ca ed negative am re-volt characteristic 2?. e., a material in w 'ch the resistance decreases with an increase of voltage or power input. A material of this character is practically essential to the construc- OOHPAINY, A C OBPOBATION OF NEW YORK.

Specification of Letters Patent.

RALPH W. ms, 02 SOEENEO'I'ADY, NEW YORK, ABSINOBTO PATENT oFFica.

GENERAL mcrnrc Patented Oct. 25, 1921.

e, 1920. Serial No. 359,953.

of curing the resistance material of my invention. h The fesistance mFteliidl of my invention as a astic ba 0 re ative y non-conducting material. :ihe material preferabl em ployed is based mainly on cement. ma-

terial based on cement whimve found may be employed with advantage has Portland cement and white river sand intimately mixed together in e usua manner substantially in the proportions of 1 2 by volume. t5 To give this material the desired .electrical "characteristics, I add to this plastic mixture cm 17 to 25 per cent. by volume of fine am black and intimately, mix this lampac roug out the mass. The lampblack preferably employed by me is obtained from crude petroleum. v

In order to get a uniform product, the resistance material made in this fashion tion of a protective reactor designed to abshould be cured in ovens in an atmos here sorb the energy of hi h fr uency transients Waised to a temperature of Between in accordance with t e disc osures of U. S. 170

ampere-volt characteristic cannot be produced uniformly in large quantities, or do not possess thecharacteristic sufiiciently acture. r By my invention, however, these difliculties are avoided. I have discovered that lampblpgkadded to a non-conducting plastic such asgncre tg in relatively small percent- F t teristic desired, gives a substantiall to suit the .particular characumform and 0001101111081 product which is very reliable when cured in the manner more fully set forth hereinafter in detail.

" --%maydetermined, and

' eentages of lampblack in resistance Y For a more complete understanding of the made in accordance with my "invention;

2 similarly shows the lawby which theperoentagesof lampblack to be emplogled Fig. 3 shows 'agrammatically'the' ,efiects of various methods L at atmos heric pres- I ould-continu'emmiter- I fiddl for a period of from 450 to 500 hours after which, as a general rule, the product should be dried out for a period of 48 hours in air at 100 C. As seen from Fig. 3, the quality of the resistance of the material so made is increased in a reliable and uniform manner and at the end of 500 hours has reached a practical max mum, which in service lasts substantially indefinitely without change.

Resistance material made in this way for percentages of lampblack varyin rom 17 to 25' as above described, under t e tension of inc voltages exhibited the socalled negative ampere-volt characteristic, as indicated by the curves drawn in Fig. 1. Here it is seen that the curves for the smaller percentages of lampblack exhibit this characteristic in the more pronounced fashion. Material having about 18% lampblack is for general use in reactors the most serviceable. 'Lam black used in percentages in excess of renders the mater al too conducting to exhibit the negative ampere-volt characteristic to any practical extent, but becomes a stable resistance.

In Fig. 21 have drawn-a curve in which resistance at a iven voltage has been lotted a tEe percentages of lamplack ,emp oyed in the mixture. Fromtbis' it is seen that the conductivity of the ancc material increases substantially in direct proportion to the percentage of lampblack em loyed. While have here disclosed a specific comsition for the resistance material of my invention which is at present the best comosition known to me, I would have it understood that this is merely illustrative and that I do not mean to be limited thereby to the exact composition disclosed, but intend to include recognized equivalents of the ingredients employed in my claims hereunto annexed.

15 What I claim as new and desire to secure by Letters Patent of the United States, is:

1, A resistance material comprising a substantially non-conducting base composed mainly of concrete and an admixture of a relatively small amount of lampblackr 2. A resistance material comprising 9.

plastic base composed mainly of concrete,

and an admixture of from 17 to per cent...

by volume of lampblack dispersed throughout the basic mass.

3. A resistance material comprising a plastic base composed mainly of cement and river sand, and an admixture of from 17 to 25 per cent. by volume of petroleum lam black intimately dispersed throughout the asic mass.

4. A resistance material having a negative ampere-volt characteristic comprising a plastic non-conducting base mainly composed of Portland cement and river sand, and an admixture of a relatively small per cent. by volume of lampblack, the whole being cured until a substantially uniform product results.

In witness whereof, I have hereunto set my hand this 17th day of February, 1920.

RAL H W. STEARNS. 

